Pyrolysis Appliance

ABSTRACT

A pyrolysis device having at least one muffle defining a cooking space and is formed with a has a muffle opening, at least one door for closing the muffle opening, and at least one drive motor for moving the door, and a self-locking gear operatively associated with the drive motor. Preferably the gear is a self-locking screw gear.

The present invention relates to a pyrolysis device, in particular a cooking appliance, specifically a high-level built-in cooking appliance, having at least one muffle that delimits a cooking space and has a muffle opening, and having a door for closing the muffle opening and a drive motor for moving the door.

Lock hooks have been known hitherto as a means for locking pyrolysis devices—which is to say domestic appliances having a pyrolytic function—that have a motorized door. Said lock hooks disadvantageously occupy space.

The object of the present invention is to provide a pyrolysis device offering a possibility of locking the door in a reliable and compact manner.

The present object is achieved by means of the pyrolysis device having the features of claim 1. Advantageous embodiments are disclosed in the subclaims in particular individually or in combination.

The pyrolysis device, in particular a high-level built-in cooking device though also a cooking appliance having an oven carriage that can be moved in a motorized manner, is for that purpose fitted with a drive motor having a self-locking gear. A mechanical pull on the door in its closed condition counter to the motor can by means of the self-locking gear be made sufficiently difficult to exert for the door to be reliably prevented from opening.

The self-locking gear is advantageously a worm gear.

It has proved favorable in the case particularly of a high-level built-in cooking appliance for the self-locking gear to have a transmission ratio in the 30:1 to 60:1 range, in particular the 40:1 to 50:1 range, specifically of 45:1. The base door of a high-level built-in cooking appliance did not move at a transmission ratio of 45:1 even under a load exceeding 20 kg.

It is generally advantageous for self-locking if the drive motor is shorted in the closed condition because an opening force must then also be exerted counter to the motor's self-induction.

The invention is described in more detail below with the aid of the embodiment variants shown in the attached schematics illustrating a high-level built-in cooking appliance. Said embodiment variants are not to be understood as limiting the invention.

FIG. 1 is a perspective view of a high-level built-in cooking appliance mounted on a wall with its base door lowered;

FIG. 2 is a perspective view of the high-level built-in cooking appliance with its base door locked shut;

FIG. 3 is a perspective view of a housing of the high-level built-in cooking appliance without the base door;

FIG. 4 is a schematic sectional side view along the line I-I shown in FIG. 1 showing the high-level built-in cooking appliance mounted on the wall with its base door lowered;

FIG. 5 is a front view of a further embodiment variant of a high-level built-in cooking appliance;

FIG. 6 is a front view of the embodiment variant shown in FIG. 5 in the closed condition with a more detailed description of the position of individual housing elements;

FIG. 7 is a sectional top view of the embodiment variant shown in FIG. 6;

FIG. 8 shows parts of the drive device for a more detailed description;

FIG. 9 is a side view, analogous to FIG. 4, of a further embodiment variant of the high-level built-in cooking appliance.

For a better presentation of the individual elements, the figures are not drawn to scale.

FIG. 1 shows a high-level built-in cooking appliance having a housing 1. The rear of the housing 1 is mounted on a wall 2 in the manner of a hanging cabinet. Defined within the housing 1 is a cooking space 3 that can be checked via a viewing window 4 provided on the front side in the housing 1. It can be seen in FIG. 4 that the cooking space 3 is delimited by a muffle 5 that is provided with a thermally insulating casing (not shown), and that the muffle 5 has a muffle opening 6 on the base side. The muffle opening 6 can be locked shut by means of a base door 7. The base door 7 is shown lowered in FIG. 1, with its being in contact at its underside with a work surface 8 of an item of kitchen equipment. To lock the cooking space 3 shut, the base door 7 must be moved to the position shown in FIG. 2, what is termed the “zero position”. For moving the base door 7 the high-level built-in cooking appliance has a drive device 9, 10 or, as the case may be, the covering thereof. The drive device 9, 10 has a drive motor 9 that is shown in FIGS. 1, 2, and 4 by dashed lines and is located between the muffle 5 and an external wall of the housing 1. The drive motor 9 is located in the region of the rear of the housing 1 and, as shown in FIG. 1 or 4, is functionally linked to a pair of lifting elements 10, for example telescopic rails, that are joined to the base door 7. Each lifting element 10 is according to the schematic side view shown in FIG. 4 therein embodied as an L-shaped support whose vertical limb extends from the drive motor 9 on the housing side.

The support is alternatively secured via a telescopic rail to the housing 1. For moving the base door 7 the drive motor 9 can be actuated with the aid of a control panel 12 and control circuit 13 located according to FIGS. 1 and 2 on the front side on the base door 7. As shown in FIG. 4, the control circuit 13 is located behind the control panel 12 inside the base door 7. The control circuit 13 which consists here of a plurality of spatially and functionally separate printed-circuit boards that communicate via a communication bus constitutes a central control unit for operating the appliance and controls and/or regulates, for example, heating, moving of the base door 3, implementing user inputs, illuminating, pinch protection, clocking of the heating elements 16, 17, 18, 22, and much else besides.

It can be seen from FIG. 1 that a top side of the base door 7 has a cooking field 15. Virtually the entire area of the cooking field 15 is occupied by heating elements 16, 17, 18 indicated in FIG. 1 by dot-and-dash lines. The heating elements 16, 17 are in FIG. 1 two spaced-apart, differently sized cooking-point heating elements while the heating element 18 is an area heating element that is provided between the two cooking-point heating elements 16, 17 and almost encloses the cooking-point heating elements 16, 17. For the user the cooking-point heating elements 16, 17 define associated cooking zones or units; the cooking-point heating elements 16, 17 along with the area heating element 18 define a bottom-heating zone. The zones can be indicated on the surface by means of a suitable decorative finish. The heating elements 16, 17, 18 can each be controlled via the control circuit 13.

The heating elements 16, 17, 18 are in the exemplary embodiment shown embodied as radiant-heat elements covered by a glass ceramic plate 19. The glass ceramic plate 11 has roughly the same dimensions as the top side of the base door 7. The glass ceramic plate 19 is furthermore provided with mounting openings (not shown) through which protrude base parts for securing fixing parts 20 for supports 21 for food being cooked, as also shown in FIG. 4. Instead of a glass ceramic plate 19 it is also possible to use other—preferably fast-reacting—covers, for example a thin metal sheet.

With the aid of a control knob provided in the control panel 12 the high-level built-in cooking appliance can be switched to a cooking-point or bottom-heating mode that will be explained below.

The cooking-point heating elements 16, 17 can in the cooking-point mode be individually controlled by means of control elements 11, which are provided in the control panel 12, via the control circuit 13, while the area heating element 18 remains non-operating. The cooking-point mode can be used with the base door 7 lowered, as shown in FIG. 1. It can, though, also be operated in an energy-saving manner with the cooking space 3 locked shut and the base door 7 raised.

Not only the cooking-point heating elements 16, 17 but also the area heating element 18 are controlled by the control device 13 in the bottom-heating mode.

In order to achieve as even as possible browning for the food being cooked during bottom-heat operation it is crucial for the cooking field 15 providing the bottom heat to distribute its heat output evenly over the surface of the cooking field 15, although the heating elements 16, 17, 18 have different rated outputs. The heating elements 16, 17, 18 are therefore preferably not switched by the control circuit 13 to continuous operation; the power supply to the heating elements 16, 17, 18 is instead clocked. The differently rated heat outputs of the heating elements 16, 17, 18 are therein individually reduced such that the heating elements 16, 17, 18 will provide a heat output that is evenly distributed over the surface of the cooking field 15.

FIG. 3 schematically shows the position of a circulating-air can 23 having a circulating-air motor and associated ring heater, for example for producing hot circulating air during a hot-air operating mode. The circulating-air can 23 that is open toward the cooking space 3 is typically separated therefrom by a baffle plate (not shown). Further provided attached to a top side of the muffle 5 is a top-heating body 22 that can be embodied as comprising one or more circuits, for example an inner and an outer circuit. The various operating modes such as, for example, also the top-heating, hot-air, or high-speed heating mode can be set by means of the control circuit 13 by appropriately activating and setting the heat output of the heating elements 16, 17, 18, 22, where applicable with the fan 23 also being activated. The heat output can be set by means of suitable clocking. The cooking field 15 can furthermore also be implemented differently, for example having or not having a fryer zone, as a pure—single-circuit or multi-circuit—warming zone without any cooking units, and so forth. The housing 1 has a seal 24 toward the base door 7.

The control panel 12 is located chiefly on the front side of the base door 7. It can alternatively conceivably also be located elsewhere, for example on the front side of the housing 1, distributed among different partial fields, and/or partially on side surfaces of the cooking appliance. Other arrangements are possible. The control elements 11 are not subject to any design constraints and can include, for example, control knobs, toggle switches, pushbuttons, and membrane switches that include the display elements 14, for example LED, LCD, and/or touchscreen displays.

FIG. 5 is a schematic showing a high-level built-in cooking appliance from the front, though not to scale, with the base door 7 open making contact with the work surface 8. The closed condition is drawn in dashed lines.

There are in that embodiment variant two movement-control panels 25 on the front side of the permanently attached housing 1. Each movement-control panel 25 has two pushbuttons, namely a top CLOSE pushbutton 25 a for a base door 7 moving upward in the closing direction and a bottom OPEN pushbutton 25 b for a base door 7 moving downward in the opening direction. Without automatic operation (see below) the base door 7 will move upward, if possible, only through continuously simultaneously pressing the CLOSE buttons 25 a on both movement-control panels 25; the base door 7 will also move downward, if possible, only through continuously simultaneously pressing the OPEN buttons 25 b on both movement-control panels 25 (manual operation). Because the user will be more attentive during manual operation and, moreover, both hands will then be used, pinch protection will in that case only be optional. Movement-control panels 26 are in an alternative embodiment variant attached to opposite external sides of the housing 1 with corresponding CLOSE buttons 26 a and OPEN buttons 26 b, as drawn with dotted lines.

The control circuit 13 which is drawn in dot-and-dash lines and located inside the base door 7 behind the control panel 12 switches the drive motor 9 such that the base door 7 will start moving gently, meaning not abruptly through simple starting of the drive motor 9 but via a defined ramp.

The control circuit 13 includes in that exemplary embodiment a memory unit 27 for storing at least one target position or moving position P0, P1, P2, PZ of the base door 7 by means preferably of volatile memory modules, for example DRAMs. When a target position P0, P1, P2, PZ has been stored, the base door can after one of the buttons 25 a, 25 b or 26 a, 26 b on respectively the movement-control panels 25 or 26 has been actuated continue moving automatically in the direction that has been set until the next target position has been reached or one of the buttons 25 a, 25 b or, as the case may be, 26 a, 26 b is actuated again (automatic operation). The bottommost target position PZ corresponds in that exemplary embodiment to the maximum opening, the (zero) position P0 corresponds to the closed condition, and P1 and P2 are freely settable intermediate positions. When the final target position for a direction has been reached it is necessary, moreover, to continue in manual operation if that is possible (meaning if the final end positions do not correspond to a maximum open or the closed end condition). If no target position has been stored for a direction—which would be the case, for example, for an upward movement into the closed position if only PZ has been stored but not P0, P1, P2—it will then be necessary analogously to proceed in that direction in manual operation. Automatic operation will not be possible if no target position has been stored, for example in the case of a new installation or following disconnection from the ac power supply. Pinch protection will preferably have been activated if the base door 7 is moved in automatic operation.

Automatic and manual operation are not mutually exclusive: Through continuous actuating of the movement-control panel(s) 25, 26 the base door 7 will also move in manual operation if a target position can be approached in the relevant direction. For example a maximum actuating time, 0.4 seconds for instance, for the movement-control panels 25 or 26 or, as the case may be, associated buttons 25 a, 25 b or 26 a, 26 b can therein be specified for activating automatic operation.

A target position P0, P1, P2, PZ can be any position of the base door 7 between and including the zero position P0 and maximum open position PZ. The maximum stored open position PZ does not, though, necessarily have to be the position in which contact is made with the work surface 8. The target position P0, P1, P2, PZ can be stored with the base door 7 at the desired target position P0, P1, P2, PZ by, for example, actuating a confirmation button 28 in the control panel 12 for a number of seconds (for example two seconds). Any existing optical and/or acoustic signal generators that feed out corresponding signals after a target position has been stored have for greater clarity been omitted from the drawing. The desired target position P0, P1, P2, PZ requiring to be set is approached by, for example, —in this exemplary embodiment—two-handedly operating the movement-control panels 25 or 26 and manually moving to said position.

Just one or, as shown in this exemplary embodiment, a plurality of target positions P0, P1, P2, PZ can be capable of being stored in the memory unit 27. When a plurality of target positions P0, P1, P2, PZ can be stored, they can be approached by consecutively actuating the corresponding movement buttons 25 a, 25 b or, as the case may be, 26 a, 26 b. Having a plurality of target positions P0, P1, P2, PZ will allow the high-level built-in cooking appliance to be accommodated conveniently to the desired operating height of a plurality of users. The target position(s) can advantageously be deleted and/or overwritten. In one embodiment variant for example only one target position can be stored in the open condition while the zero position P0 is detected automatically and can be approached automatically. The zero position P0 must alternatively also be stored to able to be approached automatically.

It is especially advantageous for insuring ergonomic use for the or a target position P1, P2, PZ to open the base door 7 at least approximately 400 mm to approximately 540 mm (meaning P1-P0, P2-P0, PZ-P0≧40 cm to 54 cm). The supports 21 for food being cooked will at that degree of opening be easy to insert into the fixing parts 20. It will be favorable therein for the viewing window 4 to be installed at approximately the user's eye level, or somewhat below it, for example by means of a template indicating the cooking appliance's dimensions.

What has not been drawn is an existing ac-power-supply buffer for bridging an approximately 1-to-3 s ac-power-supply failure, preferably one lasting up to 1.5 s.

The drive motor 9 shown in FIG. 1 has at least one sensor unit 31, 32 located, where applicable in front of or behind a gear unit, on a motor shaft 30 in order to measure a travel path or a position and/or speed of the base door 7. The sensor unit can include, for example, one or more induction, Hall, optoelectric, OFW—and so forth—sensors. Two Hall (sub-)elements 31 have for simple travel and speed measuring here been attached displaced through 180°—thus situated mutually opposite—to the motor shaft 30, and a Hall measuring sensor 32 has at a distance been stationarily attached in that region of the motor shaft. A measuring or sensor signal that is in good approximation digital will be generated if a Hall element 31 then passes by the measuring sensor 32 when the motor shaft 30 turns. So two signals will be fed out during a rotation of the motor shaft 30 if there are (though not necessarily) two Hall elements 31. The speed vL of the base door 7 can be determined by evaluating said signals on a time basis, in terms of their difference for instance, by way, for example, of comparison tables or a real-time conversion in the control circuit 13. A travel path or position of the base door 7 can be determined by adding or subtracting the measurement signals.

A speed controller can control the speed via, for example, a PWM-controlled power semiconductor.

For determining the zero point the path measurement is recalibrated automatically through initializing in the zero position P0 of the base door 7 each time a position is being approached so that, for example, a faulty sensor-signal output or reception will not propagate.

The drive motor 9 can be operated by actuating both movement-control panels 25 or, as the case may be, 26 also with the main switch 29 switched off.

Instead of two separate switches per movement-control panel 25, 26 a single switch per movement-control panel is also possible, for example a toggle switch that has a neutral position and switches only under pressure. Other forms are also possible. The manner in which the control elements 28, 29 of the control panel 12 are arranged is not limited either.

The way the control circuit 13 is arranged and disposed is therein flexible and not restricted so it can also include a plurality of boards, for example a display board, a control board, and a lifting board that are spatially separate.

A 4-mm opening extent can be detected by end switches 33 which on actuation deactivate pinch protection.

The high-level built-in cooking appliance can also be embodied without a memory unit 27, with automatic operation then not being possible. That can be expedient for enhanced operating safety, for example as a protection against pinching.

FIG. 6 is a schematic front view (not to scale) of the position of individual elements of the housing 1 in the closed condition in which the base door 7 closes against the muffle 5 and thereby also forms an optical closure of the housing 1. The housing 1 consists of an (inner) housing body 34 (shown in dashed lines) and a housing cover or panel 35 that surrounds the housing body 34 at least at the front and sides. The space 36 between the housing body 34 and housing cover 35 is embodied in such a way that cooling air can at least partially flow through. Provided therefor in the housing cover 35 are bottom ventilation openings 37, for example ventilation slits, positioned lower than the top surface 38 of the housing body 34 preferably in a region close to the muffle opening or lifting base 7. The ventilation openings 37 are here provided on the underside of the housing cover 35, but they can also be provided laterally, for example. There are correspondingly one or more top venting openings 39, for example a venting slit, in the top part of the housing cover 35, specifically in its ceiling. A current of cooling air can thereby be set up, typically from bottom to top, through the space 36, which current is then ducted away through the ceiling.

The muffle 5 (shown in dotted lines) is emplaced in the housing body 34, with the associated space 40—except for the front side—being lined with insulating material. The muffle 5 is embodied shaped like an inverted U. Provided to afford a view into the cooking space 3 are a plurality of viewing windows 4, namely a first (inner) viewing window 41 (indicated by dot-and-dash lines) which directly covers the muffle 5 and hence constitutes at least partially a wall of the muffle 5, a second (middle) viewing window 42 (indicated likewise by dot-and-dash lines) held in position by the housing body 34, and a third (outer) viewing window 43 in the housing cover 35.

It is optionally possible to include further intermediate windows (not shown) secured preferably to the housing body 34, or there can be fewer viewing windows 4, for example only the inner and outer viewing window 41, 43. The venting slits 37, 39, for example, can also be provided arranged otherwise and in another form.

As a top view onto the housing 1 corresponding to the sectional plane III-III shown in FIG. 6 (meaning without a top housing wall), FIG. 7 is a detailed view (not to scale) of the inside of the housing with various elements located there. The spaces 36 between the housing body 34 and housing cover 35, namely the lateral spaces 44, the front space 45, and the rear space 46, can clearly be seen from that view. The front space 45 is owing to the three viewing windows 41, 42, 43 subdivided vertically into a first front space 45 a between the middle viewing window 42 and outer viewing window 43 and a second front space 45 b between the middle viewing window 42 and inner viewing window 41. The spaces do not have to be empty, of course, but can contain various elements such as, for example, lifting elements 10, support means, passages, insulating means, air-ducting elements such as air baffles, screws, and struts etc., with not every space 36 having necessarily to allow a significant current of air.

Attached to the housing body 34 are in particular: Electric or electronic modules 47 such as the control circuit 13, a drive device 48, and a ventilating device 49.

The ventilating device 49 includes at least one fan which in this embodiment variant is precisely one fan that sucks in air from two directions by means of two suction openings. Advantageously used for that purpose is a two-part fan in the case of which the discharged air is fed out additionally at least substantially in unmixed form. The double radial fan 50 shown here that has two opposite suction openings and feeds out sucked-in air laterally is especially suitable. The two sucked-in air streams are therein fed out substantially laterally mutually parallel.

A suction opening of the double radial fan 50 is in the structural variant shown here linked to a suction channel 51 that at least partially covers the front space 45 from above and during operation thereby sucks in cooling air from below from the bottom venting openings 37 through the front space 45. The front space 45 which owing to the viewing windows 4, 41-43 provides thermal insulation that is rather on the low side is thereby cooled for better user safety.

The other (rear) suction opening of the double radial fan 50 is open. Cooling air is consequently sucked in particularly from the lateral spaces 44 and rear space 46 and flows over the top surface 38 to the fan 50. The components located on the top surface 38 will consequently also be cooled through air flowing around or through them. That is advantageous particularly for the electronic modules 47.

The air discharged from the fan 50 passes through an air-discharge channel 52 to a top air outlet 53 which blows out the air through the venting opening(s) 39 shown in FIG. 6.

The drive device 48 includes a motor 9 that is secured centrally on the surface 38 of the housing body 34 and on top of which is a guide housing 54. Two guide channels (not shown). pass through the guide housing 54. The guide housing 54 has a circular recess for inserting a pinion 55 of the motor 9. The guide channels pass laterally open by the recess so that any ropes, cables etc. in the guide channels will be brought into engagement with the pinion 55. Attached to the guide channels' outer openings, thus in this case four openings, are guide tubes 56 which together with the guide channels form continuous cable channels. The guide tubes 56 extend in that embodiment variant from the guide housing 54 to the edge of the top surface 38 into a region above the lifting elements 10 then over the edge downward into the lifting elements 10.

Extending through each of the two cable channels as a pitch cable is a drive cable (not shown). The pitch cable has a flexible metal core and is wire-covered. One end of each pitch cable is permanently joined to the base door 7; the other is free. Because both pitch cables engage on opposite sides with the pinion 55, they will be linearly displaced in opposite directions through turning of the pinion 55. The pitch cable drive can be obtained from, for instance, the company WEBASTO, Germany.

The guide tubes 56 are elastically deformable, being shaped from, for example, die-cast aluminum. At least one load-bearing guide tube 56 (which is to say a guide tube 56 that ducts a section of a pitch cable which is permanently joined—directly or indirectly—to the base door 7; a load is thereby applied to that section of the pitch cable) is supported on a bearing surface 57, with the bearing force depending on the size of the load on the pitch cable. A bearing surface 57 of such type is in that embodiment variant provided for each load-bearing guide tube 56. The bearing surfaces 57 are located substantially on the edge of the top surface 38 of the housing body 34 so that the length of the guide tube 56 deflectable under load—its “arm”—becomes large. The load dependency of the substantially vertical force exerted by the respective guide tube 56 on the bearing surface 57 will as a result be embodied as being as great as possible. The bearing force is dependent on, for example, the extent to which the base door 7 is loaded or on a settling onto a base or object. Overload-detection for the base door 7 or pinch protection, for example, can be realized by measuring the bearing force.

The length of the guide tubes 56 is a discretionary design-related matter and can be relatively short or can extend as far as where the pitch cable is secured to the base door 7 (in the closed condition).

Although the use of guide tubes 56 for allowing the pitch cables' bearing surface to be employed for load measuring is for reasons relating to gliding and abrasion advantageous it is not essential. It is possible also to duct the pitch cables—or cables or ropes in general—freely via suitably positioned bearing surfaces (for example ones extending beyond the surface edge). The bearing surfaces will then be favorably embodied appropriately, being made from, for example, a suitable hard material and/or one capable of gliding, having a treated or coated surface.

Nor is the use of a pitch cable drive essential, though advantageous owing to its simple structural design and installation as well as precise displacement. Alternative drives include, for instance, such that drive a rope drum etc.

For a more detailed description of the drive principle, FIG. 8 is a top view of the guide housing 54 with the connected guide tubes 56 forming two separate guide channels, namely—in that representation—a top and a bottom guide channel. Extending through each of the guide channels 54, 56 is a pitch cable 58 typically around one meter in length. The guide channels direct the pitch cables 58 to a recess in the guide housing 54 through which a toothed wheel or pinion 55 driven by the drive motor has been passed. The teeth of the pinion 55 engage with the wound wire of the respective pitch cable 58 which from the viewpoint of the pinion 55 forms a kind of linear sequence of teeth.

The top pitch cable 58 is moved linearly from left to right through turning of the pinion 55 by means of the drive motor—in this case clockwise, shown by the unbroken arrows—and the bottom cable 58 is moved in equal measure from right to left, as indicated by the dashed arrows.

Because the pitch cables 58 engage permanently with the pinion 55 and so are continuously coupled to the drive motor, effective locking of the base door in the opening direction can also be achieved, for example for protecting against opening of a hot cooking space, for example during pyrolysis, or when the child-safety facility has been activated. What has been used hitherto for door locking is a mechanical lock that locks the door as a function of specific parameters such as a threshold temperature etc. by means typically of a lock hook. It is, though, possible to dispense with a lock of said type if the drive motor according to, for example, the reference numeral 9 in FIG. 7 drives the pinion 55 via a self-locking gear (not shown). When the drive motor has been switched off—effected preferably by switching off the power supply and deactivating direction switches—a mechanical force and an induction force of the drive motor will have to be overcome for opening the cooking space or generally for moving the base door. The force applied to do so must be the greater the higher the gear's transmission ratio is. A transmission ratio in the 30:1 to 60:1 range has for the embodiment variant shown proved to be a good compromise between self-locking and speed of travel. In particular a transmission ratio in the 40:1 to 50:1 range, specifically of 45:1, is suitable. At a transmission ratio of 45:1 the base door could not be opened under a load exceeding 20 kg.

FIG. 9 is a side view, analogous to FIG. 4, of a further embodiment variant of the high-level built-in cooking appliance with a more detailed description of the drive device shown in FIGS. 7 and 8. The drive motor 9, the guide housing 54, the ventilating device 49, and the electronic modules 47 have for greater clarity been omitted from the drawing. The other side of the cooking appliance is constructed analogously.

The elastically deformable guide tubes 56 can be seen that are at the top supported by the bearing surface 57 and then extend bent downward into the lifting elements 10. The pitch cables 58 exit from the free openings of the guide tubes 56, namely a section—bearing a load on that side—of a pitch cable 58 (left) that is permanently joined via a securing element 59 to the bottom telescopic 20 rod 60 of the lifting element 10 and hence indirectly to the base door 7. The other (right-hand) pitch cable 58 has on that side a free end. On the other side of the cooking appliance the respectively other pitch cable 58 is secured or, as the case may be, free. The pitch cables 58 will, as described above, be linearly displaced through actuating of the drive motor and raise or, as the case may be, lower the base door 7.

Any excess pressure produced within the cooking space as a result of pyrolytic deflagration can be suitably released by, for example, briefly opening an opening, for instance a ventilator valve or suchlike. It is also basically possible when a pre-specified internal pressure is exceeded for the door of the pyrolysis device to briefly open through, for example, the brief overcoming of a closing force, for example an elastic force, by the internal pyrolytic pressure.

LIST OF REFERENCE NUMERALS/LETTERS

-   1 Housing -   2 Wall -   3 Cooking space -   4 Viewing window -   5 Muffle -   6 Muffle opening -   7 Base door -   8 Work surface -   9 Drive motor -   10 Lifting element -   11 Control element -   12 Control panel -   13 Control circuit -   14 Display elements -   15 Cooking field -   16 Cooking-point heating element -   17 Cooking-point heating element -   18 Area heating element -   19 Glass ceramic plate -   20 Fixing part -   21 Support for food being cooked -   22 Top-heating body -   23 Fan -   24 Seal -   25 Movement-control panel -   25 a Movement switch, upward -   25 b Movement switch, downward -   26 Movement-control panel -   26 a Movement switch, upward -   26 b Movement switch, downward -   27 Memory unit -   28 Confirmation button -   29 Main switch -   30 Motor shaft -   31 Hall element -   32 Measuring sensor -   33 End switch -   34 Housing body -   35 Housing cover -   36 Space -   37 Bottom venting openings -   38 Top surface of the housing body (34) -   39 Top venting opening -   40 Space -   41 First (inner) viewing window -   42 Second (middle) viewing window -   43 Third (outer) viewing window -   44 Lateral spaces -   45 Front space -   45 a First front space -   45 b Second front space -   46 Back space -   47 Electric or electronic modules -   48 Drive device -   49 Ventilating device -   50 Fan -   51 Suction channel -   52 Air-discharge channel -   53 Air outlet -   54 Guide housing -   55 Toothed wheel -   56 Guide tubes -   57 Bearing surface -   58 Pitch cable -   59 Bottom telescopic rod -   60 Pitch cable fastening -   61 Top telescopic rod -   P0 Zero position -   P1 Intermediate position -   P2 Intermediate position -   PZ End position 

1-6. (canceled)
 7. A pyrolysis device having at least one muffle defining a cooking space and is formed with a has a muffle opening, at least one door for closing the muffle opening, and at least one drive motor for moving the door, the pyrolysis device comprising a self-locking gear operatively associated with the drive motor.
 8. The pyrolysis device according to claim 7 wherein the self-locking gear is formed as a worm gear.
 9. The pyrolysis device according to claim 7 wherein the self-locking gear has a gear ratio of about 30:1 to about 60:1.
 10. The pyrolysis device according to claim 9 wherein the self-locking gear has a gear ratio of about 40:1 to about 50:1, in particular about 45:1.
 11. The pyrolysis device according to claim 7 wherein the drive motor is shorted when the door is in the closed condition.
 12. The pyrolysis device according to claim 7 wherein the pyrolysis device is formed as a cooking appliance, in particular a high-level built-in cooking appliance having a muffle opening formed in a base door. 